Differential Compaction and its Effects on the Outer Shelf of the Permian Capitan Reef Complex, Guadalupe Mountains, New Mexico
Andrew J. Longley, 1999. "Differential Compaction and its Effects on the Outer Shelf of the Permian Capitan Reef Complex, Guadalupe Mountains, New Mexico", Geologic Framework of the Capitan Reef, Arthur H. Saller, Paul M. (Mitch) Harris, Brenda L. Kirkland, S. J. Mazzullo
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The outer shelf sediments of the Capitan Reef Complex (Permian, Guadalupian) dip towards the basin at variable angles of up to 10°. High-resolution correlation of field logs from several canyons in the Guadalupe Mountains, New Mexico, has revealed a geometry that is most likely to have resulted from differential subsidence with the greatest rate of subsidence occurring at the shelf margin. During deposition of the upper Seven Rivers, Yates, and lower Tansill Formations, the reef accreted in several alternating phases of progradation and aggradation in response to fluctuating sea level. As the reef aggraded, loading of the underlying fore-reef and basin deposits gave rise to episodic compaction-induced differential subsidence, which tilted the outer shelf strata in a basinward direction. This process was controlled by the variable compactability of the forereef and basin lithologies as well as by the loading of the aggrading reef. Episodic differential compaction also influenced deposition of outer shelf sediments and induced small-scale relative sea-level changes near the shelf margin that were not experienced by the inner shelf. Mechanical failure of lithified outer shelf sediments occurred as the reef prograded over the compacting fore-reef and basin deposits. Water and liquefied sand from compacting basin sediments appear to have been forcefully injected upwards through mechanically initiated fractures, and the effects of dissolution are apparent along some fracture margins. The importance of differential compaction as a control on platform development must be recognized if the effects of sea level are to be properly understood.
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The Capitan Formation of southeast New Mexico and west Texas contains one of the world's best exposed and most famous reefs. Depositional and diagenetic models derived from the Capitan have been used to interpret carbonate strata throughout the world. This volume contains 12 state-of the- art papers summarizing major new research on the Capitan, putting the Capitan into a modern statrigraphic, depositional, paleontologic, and diagenetic framework.